Method of manufacturing a connecting rod assembly for an internal combustion engine

ABSTRACT

A method of manufacturing a connecting rod assembly including the steps of defining a small end of a connecting rod assembly having a terminal end and then defining a pin bore extending through the small end of the connecting rod assembly. A pair of channels is formed on opposite sides of the small end of the connecting rod assembly wherein the axis of each of the channels is substantially perpendicular to the axis of the pin bore. A bushing having a contact surface including at least partially annular grooves disposed thereon is installed into the pin bore of the small end. The connecting rod is then machined to reduce the width of the small end between each channel and the terminal end wherein at least a portion of the grooves are disposed along the distal ends to reduce the need to deburr the area adjacent to the pin bore.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. Ser. No. 12/356,110 entitled“Method of Manufacturing a Connecting Rod Assembly for an InternalCombustion Engine” filed Jan. 20, 2009, which is a divisional of U.S.Ser. No. 10/989,633, entitled “Connecting Rod Assembly for an InternalCombustion Engine and Method of Manufacturing Same” filed Nov. 16, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates, generally, to connecting rod assembliesand, more specifically, to a method of manufacturing a connecting rodassembly for an internal combustion engine.

2. Description of the Related Art

Internal combustion engines known in the related art may generallyinclude, among other basic components, an engine block having one ormore cylinders, cylinder heads associated with the engine block, pistonssupported for reciprocal movement in each cylinder, and connecting rodassemblies to transfer the movement of the pistons to the crankshaft.The piston generally includes a bore that corresponds to a similar pinbore at one end of the connecting rod assembly. A pin is placed throughthe corresponding bores to attach the piston to the connecting rodassembly. The end of a connecting rod assembly having the pin bore iscommonly referred to as the “small end.” The other end of a connectingrod assembly is fastened to the crankshaft at a particular location.This end of the connecting rod assembly is commonly referred to as the“crank end” or “large end.”

Generally, fuel is combusted within the cylinders to reciprocate thepistons. The piston drives the connecting rod assembly, which drives thecrankshaft, causing it to rotate within the engine block. Specifically,as fuel is combusted within the cylinder, the combustion pressure drivesthe piston downward in a substantially linear motion, which in turndrives the connecting rod assembly in a substantially linear, butslightly rotational motion. On the other hand, the large end of theconnecting rod assembly is attached to the crankshaft, which drives thelarge end of the connecting rod assembly in a substantially rotationalmotion.

Since it is the connecting rod assembly that transfers the reciprocalmotion of the piston into the rotational motion of the crankshaft, theconnecting rod assembly incurs a high level of stress at both the largeend and small end pivot points. At the small end, the lower surface ofthe pivot point has to resist a high load from the transfer of thecombustion pressure from the piston pin down through the connecting rod.The upper surface of the connecting rod at the small end has to resist amuch lower load, which is the result of inertia force from thereciprocating masses during the exhaust stroke.

To optimize efficiency in this location, the small end of the connectingrod assembly may be manufactured to have a reduced width at the upperregion with respect to the remaining portion of the small end. One typeof connecting rod assembly that has a reduced width small end iscommonly referred to as a “stepped” connecting rod assembly.Specifically, the reduced width small end of a connecting rod assemblypermits a wider bearing area in the piston and increases the overallload carrying capability while minimizing the overall weight of thepiston and connecting rod assembly.

However, in order to provide a stepped connecting rod assembly, aportion of the small end between the pin bore and the upper region isremoved by a machining process. The machining process generates burrsalong the edges, such as around the pin bore, which must be removedprior to assembling the connecting rod assembly to the piston. Thedeburring imposes an additional step in the manufacturing process thatis costly and labor-intensive. Yet, without the deburring process,excess material along the small end may prevent proper assembly of theconnecting rod assembly to the piston pin or other components of theengine. Additionally, the excess material may fragment from theconnecting rod assembly during engine operation, which can cause enginefailure.

In addition to providing a stepped configuration to facilitate loadcarrying capacity and seizure resistance, connecting rod assemblies mayalso employ a bushing within the pin bore of the small end to accomplisha similar objective. A bushing at this location is often constructedfrom a dissimilar material to that of the connecting rod assembly toreduce friction and provide smooth angular movement along the pivotpoint, thereby reducing scuffing which can cause engine damage. As aresult, it is often desirous to employ a bushing at the small end of theconnecting rod assembly. However, the addition of a bushing within thesmall end does not eliminate the need for the small end to undergo adeburring process after machining to provide a reduced widthconfiguration.

Furthermore, moment forces are generated during installation of abushing at the small end of a connecting rod assembly where the upperregion of the small end has a reduced width with respect to theremaining portion of the small end. Specifically, during installation,the non-planar area around the pin bore of the stepped small end causesthe bushing to shift in a manner where the bushing is no longer parallelwith the pin bore. This can result in misalignment between the bushingand pin bore or deformation of the bushing, creating irregular contactbetween the bushing and the pin bore, which may lead to prematurebushing failure. Additionally, this misalignment can translate to anirregular bushing surface that contacts the piston pin, which maypromote scuffing and lead to engine damage.

Moment forces are also generated during the machining of the surfacewithin the pin bore of the small end of a connecting rod assembly thatcontacts a piston pin. This is especially true where the connecting rodassembly has a stepped small end whether or not a bushing is employedwithin the pin bore. Specifically, the non-planar area around the pinbore of the stepped small end may permit the machining tool to shiftwhile it is cutting and defining the contact surface. This shift has atendency to create a concave lower surface, which reduces optimumefficiency at this pivot point. The creation of such a non-uniformcontact surface may lead to premature failure of the pivot point betweenthe contact surface and the piston pin, which can lead to engine damage.

The irregularities caused by the moment forces associated withinstalling a bushing in the pin bore of stepped small end of aconnecting rod assembly as well as those associated with machining thecontact surface in the pin bore are detrimental to the efficiency andcost-effectiveness of manufacturing connecting rod assemblies. Notably,these irregularities impose additional steps in the manufacturingprocess to inspect connecting rod assemblies and correct theirregularities where appropriate, which increases costs associated withadditional labor, additional machining and lost manufacturing. Further,these irregularities can cause an out-of-tolerance condition, renderingthe entire connecting rod assembly unusable.

As a result, there is an ongoing need in the art to improve connectingrod assemblies and the method of manufacturing connecting rodassemblies, in general. Specifically, there is an ongoing need tostreamline the manufacturing process while retaining strength andacceptable product life of connecting rod assemblies having a steppedsmall end. Thus, there continues to be a need in the art for a method ofmanufacturing a connecting rod assembly that essentially eliminates thedeburring process at the small end. Further, there is a need in the artto provide a method of manufacturing a connecting rod assembly thatessentially eliminates moment forces that occur when the bushing isinstalled within the pin bore of a stepped small end of a connecting rodassembly as well as the moment forces that occur when a contact surfaceis machined in the stepped small end of a connecting rod assembly.

SUMMARY OF THE INVENTION

The present invention overcomes the disadvantages in the related art ina method of manufacturing a connecting rod assembly for use with aninternal combustion engine. The method includes the steps of compressingmetal powder within a die cavity defining the predetermined form,sintering the compressed the powder to bond and conform to thepredetermined form of the die cavity such that the metal powder isshaped into a connecting rod and removing the connecting rod from themold cavity. In addition, the method also includes the steps of defininga pin bore extending through the small end of the connecting rod andforming a pair of channels on opposite sides of the small end of theconnecting rod wherein the axis of each of the channels is substantiallyperpendicular to the axis of the pin bore. A bushing is formed having acontact surface including at least partially annular grooves disposedthereon and opposed distal ends. A bushing is installed into the pinbore of the small end. In addition, the connecting rod is machined toreduce the width of the small end between each channel and the terminalend wherein at least a portion of the grooves are disposed along thedistal ends to reduce the need to deburr the area adjacent to the pinbore.

Accordingly, one advantage of the present invention is it streamlinesmanufacturing by essentially eliminating the need for a deburringprocess after the small end of the connecting rod is machined to areduced width configuration.

Still another advantage of the present invention is that it reduces themoment forces generated when installing a bushing into a pin bore of astepped small end of a connecting rod, thereby reducing the likelihoodof deforming the bushing and creating an irregular contact area betweenthe bushing as well as the pin bore and the bushing and the piston pin.

Still another advantage of the present invention is that it reduces themoment forces generated when defining a contact surface within the pinbore of a stepped small end of a connecting rod assembly that receives apiston pin, thereby reducing the likelihood of deforming the distal endsof the contact surface and creating an irregular pivot point between thecontact surface and the piston pin.

Still another advantage of the present invention is that it streamlinesthe manufacture of a connecting rod assembly by reducing the need forinspecting and correcting irregularities caused by moment forcesgenerated during installation of a bushing.

Still another advantage of the present invention is that it streamlinesthe manufacture of a connecting rod assembly and connecting rod assemblyby reducing the need for inspecting and correcting irregularities causedby moment forces generated during machining to define a contact surfacewithin the small end that engages a piston pin.

Other objects, features, and advantages of the present invention will bereadily appreciated, as the same becomes better understood, afterreading the subsequent description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional environmental view of an internal combustionengine including a connecting rod assembly manufactured pursuant to themethod of the present invention.

FIG. 2 is an enlarged cross-sectional view of the connecting rodassembly manufactured pursuant to the method of the present inventionand shown secured to a piston.

FIG. 3A is an exploded, fragmentary cross-sectional view of the smallend of the connecting rod assembly with formed channels but prior toinstallation of a bushing and final machining, with the final machininglines shown in phantom, in accordance with the present invention.

FIG. 3B is a fragmentary cross-sectional view of the small end of theconnecting rod assembly after the bushing has been inserted but prior tofinal machining with the final machining lines shown in phantom inaccordance with the present invention.

FIG. 4 is a fragmentary cross-sectional view of the small end of theconnecting rod assembly and illustrating a machining tool to define acontact surface in the small end that engages a piston pin manufacturedpursuant to the method of the present invention.

FIG. 5A is a fragmentary cross-sectional view of the small end of theconnecting rod assembly manufactured pursuant to the method of thepresent invention.

FIG. 5B is a fragmentary perspective view of the small end of theconnecting rod assembly of FIG. 5A manufactured pursuant to the methodof the present invention.

FIG. 6 is a fragmentary cross-sectional view of a small end of aconnecting rod assembly having a bushing manufactured pursuant toanother method of the present invention.

FIG. 7 is a fragmentary perspective view of yet another embodiment ofthe small end of the connecting rod assembly manufactured pursuant toyet another method of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A connecting rod assembly manufactured pursuant to the method of thepresent invention is generally indicated at 10 throughout the figures,where like numbers are used to designate like structures throughout thedrawings. As shown in FIG. 1, the present invention is particularlyadapted for use in an internal combustion engine, generally indicated at12. In this case, the assembly 10 of the present invention isillustrated in connection with a single cylinder 14 of an internalcombustion engine 12 having a dual-overhead cam arrangement. Thosehaving ordinary skill in the art will appreciate that the engine 12 isbut one of the many internal combustion engines with which the presentinvention may be employed. By way of example, the present invention maybe employed to manufacture a connecting rod assembly used in atwo-stroke or four-stroke engine. The cylinders may be arranged in anin-line, v-shaped, or flat manner or in any other manner commonly knownin the art. The present invention may also be employed with a carburetedor fuel injected internal combustion engine having single or dualoverhead or undermounted cam(s).

With continuing reference to FIG. 1, the internal combustion engine 12includes an engine block 16 having one or more cylinders 14, and acylinder head generally indicated at 18 associated with the engine block16. Rocker panels 20 are associated with the cylinder head 18 in amanner commonly known in the art. A piston, generally indicated at 22,is supported for reciprocal movement in a cylinder 14. The connectingrod assembly 10 is secured to the piston 22 through a piston pin 24 aswill be explained in greater detail below. A crankshaft 26 is associatedwith the connecting rod assembly 10 and an oil pan 28 is associated withthe engine block 16. An intake valve 30 and an exhaust valve 32, eachhaving valve stems 34 and valve springs 36 are supported in the cylinderhead 18 and are opened and closed via cams 38 to provide fluidcommunication between the cylinder 14 and the intake valve 30 and theexhaust valve 32. The internal combustion engine 12 also includes aspark plug 40 for igniting the fuel within the combustion chamber 42defined by the cylinder walls 44 and above the piston 22. Alternatively,or in addition, the engine 12 may include a fuel injector (not shown) asa means of introducing atomized fuel into the combustion chamber 42.Thus, the present invention may be employed in connection with both aspark ignition or compression ignition (diesel) engine. Those havingordinary skill in the art will appreciate that the engine 12 alsoincludes a number of other conventional components that are commonlyknown in the art and that will not be described in detail here.

Generally, fuel is combusted within the combustion chamber 42 of acylinder 14 to reciprocate the piston 22. The piston 22 drives theconnecting rod assembly 10, which drives the crankshaft 26, causing itto rotate within the engine block 16. Specifically, the combustionpressure within the cylinder 14 drives the piston 22 downward in asubstantially linear, but slightly rotational motion. On the other hand,movement of the crankshaft 26 drives the connecting rod assembly 10 in asubstantially rotational motion.

As shown in FIG. 2, the piston 22 includes a body 46 having a crown 48formed at the uppermost margins of the body 46 and a skirt 50 dependingfrom the crown 48. Ring lands 52 extend about the outer circumference ofthe body 46 between the crown 48 and the skirt 50. The ring lands 52 areadapted to retain piston rings (not shown, but generally known in theart). The body 46 further includes a bore 54 formed therein. The bore 54is adapted to receive the piston pin 24. The piston pin 24 is oftencylindrical in shape and includes a substantially uniform diameter. Thisshape has been adopted as the standard for most applications. However,those having ordinary skill in the art will appreciate that the pistonpin 24 may include a center area having a reduced diameter with respectto the diameter of the distal ends. Accordingly, those having ordinaryskill in the art will appreciate that the bore 54 will include a shapethat corresponds to the shape of the piston pin 24. Furthermore, thosehaving ordinary skill in the art will appreciate that pistons can havemany different shapes, sizes, and other structural features. By way ofexample, the pistons 22 may include any number of ring lands 52, orprotrusions and/or recesses on the crown 48 for facilitating thecombustion process and enhancing the power or efficiency derivedtherefrom. The piston 22 may also include recesses or grooves formed onthe piston skirt 50 or a coating applied to the piston skirt 50.

As mentioned above, the connecting rod assembly 10 is adapted tointerconnect the piston 22 and the crankshaft 26 so as to translate thereciprocal movement of the piston 22 into rotational movement of thecrankshaft 26. To this end, the connecting rod assembly 10 includes asmall end, generally indicated at 56, secured to the piston 22 via thepiston pin 24 and a large or crank end 58 operatively secured to thecrankshaft 26 through bolts 60. The small end 56 includes a terminal end62 and a pin bore, generally indicated at 64, extending therethrough.The pin bore 64 is adapted to receive the piston pin 24. As describedabove, the piston pin 24 may include a number of different shapes whichdepart from the standard cylindrical shape used in most applications.Accordingly, those having ordinary skill in the art will appreciate thatthe pin bore 64 of the connecting rod assembly 10 will accommodate shapeof piston pin 24 employed for a particular application.

Referring to FIGS. 3A and 3B, the connecting rod assembly 10manufactured according to the method of the present invention includes apair of channels, generally indicated at 68 and 70, formed on oppositesides 72, 74 of the small end 56. The sides 72, 74 on which the channels68, 70 are located are the sides through which the pin bore 64 extends,such that the axis of each of the channels 68, 70 is substantiallyparallel to each other and perpendicular to the axis of the pin bore 64.Each of the channels 68, 70 includes a pair of ridges 76, 78, 80, 82 onopposite sides of the pin bore 64. The ridges 76, 78 and 80, 82 for eachchannel 68, 70 respectively, are coplanar to reduce or eliminate anymoment force that may be generated when a bushing, to be described ingreater detail below, is installed into the pin bore 64, therebyreducing misalignment between the bushing and pin bore and deformationof the bushing. Additionally, the ridges 76, 78, 80, 82 reduce oreliminate any moment force that may be generated when the contactsurface within the small end 56 is defined by machining or otherwise, aswill be described in greater detail below.

The connecting rod assembly 10 may also include a bushing, generallyindicated at 84. The bushing 84 includes a predetermined outer diameterto facilitate installation of the bushing 84 in a fixed position withinthe pin bore 64, as will be described in greater detail below. Thebushing 84 may include predetermined contours 86, 88 which substantiallycorrespond to the contour of the opposed channels 68, 70 respectively,as shown in FIG. 3B. On the other hand, the bushing 84 that does nothave predetermined contours, as shown in FIG. 3A, may also be employed.

Referring to FIGS. 3A-6, the bushing 84 further includes a contactsurface 90 that is disposed for rotational contact with the piston pin24, thereby interconnecting the connecting rod assembly 10 to the piston22. The contact surface 90 defines a pivot axis about which the pistonpin 24 may rotate during movement of the piston 22 and connecting rodassembly 10 within the cylinder 14. To perform the desired objectives ofcountering high loads, facilitating load carrying capacity and resistingseizure, the bushing 84 may be constructed from a metal that isdissimilar from that of the connecting rod assembly 10, which reducesfriction and scuffing that might otherwise occur between the piston pin24 and the pin bore 64. However, those having ordinary skill in the artwill appreciate that a bushing 84 constructed from a polymer may also beemployed to accomplish a similar end, where the polymer material issuitable for use within an internal combustion engine 12. Further, thebushing 84 may be constructed from a rolled material or flat stockmaterial and subsequently worked to provide the substantiallycylindrical shape corresponding to the inner circumference of the pinbore 64.

The contact surface 90 of the bushing 84 further includes at least apair of grooves 92, 94 and opposed distal ends 96, 98, as shown in FIG.3A. Where the bushing is constructed from a flat stock material thegrooves may be machined prior to working the material to correspond tothe inner circumference of the pin bore 64. The grooves 92, 94 mayextend for a predetermined annular extent about the contact surface 90.However, the grooves 92, 94 may also extend entirely around thecircumference of the contact surface 90, as shown in FIG. 3B. In eitherevent, the grooves 92, 94 are disposed along at least a portion of thedistal ends 96, 98 (FIGS. 5A and 5B), thereby essentially eliminatingthe need to deburr the small end after machining to provide a reducedwidth configuration, as will be described in greater detail below. Thegrooves 92, 94 may also facilitate lubrication during engine operationto reduce friction and thermal stress at the interface between thepiston pin 24 and the contact surface 90 of the bushing. Those havingordinary skill in the art will appreciate that while the grooves 92, 94are disposed on only a portion of the distal ends 96, 98, they may bedisposed along the entire distal ends.

Referring to the embodiment illustrated in FIGS. 2-5B, the small end ofthe connecting rod assembly 10 includes a stepped configuration.However, there exist situations where it is desirous to employ aconnecting rod assembly having a reduced width design other than astepped configuration. Accordingly, another connecting rod assemblymanufactured according to the method of the present invention isgenerally indicated at 110 in FIG. 6 where like numerals, increased by100 with respect to the embodiment of the invention illustrated in FIGS.2-5B, are used to designate like structure. The connecting rod assembly110 is similar to the connecting rod assembly 10 shown in FIGS. 2-5 andso the description of the illustrated structure will not be repeatedhere except where expressly mentioned below.

Referring to FIG. 6, the connecting rod assembly 110 is shown having asmall end 156 including a terminal end 162 and pin bore 164 extendingtherethrough. In this embodiment, the small end 156 includes atrapezoidal configuration. In this embodiment, the connecting rodassembly 110 also includes a bushing, generally indicated at 184. Thebushing 184 includes a predetermined outer diameter to facilitateinstallation in a fixed position within the pin bore 164, as describedin greater detail below. The bushing 184 further includes a contactsurface 190 that is disposed for rotational contact with the piston pin24, thereby interconnecting the connecting rod assembly 110 to thepiston 22.

The contact surface 190 of the bushing 184 further includes at least apair of grooves 192, 194. The grooves 192, 194 may extend for apredetermined annular extent about the contact surface 190. However, thegrooves 192, 194 may extend entirely around the circumference of thecontact surface 190, as shown in FIG. 6. In either event, at least aportion of the grooves 192, 194 are disposed along the distal ends 196,198 to essentially eliminate the need to deburr the small end 156 of theconnecting rod assembly 110 after machining to create the trapezoidalconfiguration, as described in greater detail below. As further shown inFIG. 6, the grooves are annularly disposed along the entirecircumference of the distal ends 196, 198. The grooves 192, 194 may alsodirect lubrication during engine operation to reduce friction andthermal stress at the interface between the piston pin 24 and thecontact surface 190 of the bushing 184.

In the embodiments illustrated in FIGS. 2-6, the connecting rod assembly10, 110 includes a bushing 84, 184. However, there exist situationswhere it is desirous to employ a connecting rod assembly without abushing 84, 184. Accordingly, another connecting rod assemblymanufactured according to the method of the present invention isgenerally indicated at 210 in FIG. 7 where like numerals, increased by200 with respect to the embodiment of the invention illustrated in FIGS.2-5B, are used to designate like structure. The connecting rod assembly210 is similar to the connecting rod assembly 10 shown in FIGS. 2-5B andso the description of the illustrated structure will not be repeatedhere except where expressly mentioned below.

Referring to FIG. 7, the connecting rod assembly 210 is shown having asmall end 256 including a terminal end 262 and pin bore 264 extendingtherethrough. In this embodiment, the inner circumference of the pinbore 264 is substantially cylindrical. However, those having ordinaryskill in the art will appreciate that the inner circumference of the pinbore 264 may also define a number of other shapes. By way of example,the inner circumference of the pin bore 264 may be substantially oval orinclude a tapered profile to accommodate a particular style of pistonpin 24. The pin bore 264 further includes a contact surface 290operatively engaged by the piston pin 24, thereby interconnecting theconnecting rod assembly 210 to the piston 22. The contact surface 290 isdefined to provide a pivot surface between the connecting rod assembly210 and the piston pin 24 to facilitate smooth linear and rotationalmovement of same within the cylinder 14 during engine 12 operation. Thecontact surface 290 includes at a pair of grooves 292, 294 and opposeddistal ends 296, 298. The grooves 293, 294 may extend for apredetermined annular extent about the contact surface 290. However, thegrooves may also extend entirely around the circumference of the contactsurface 290, as shown in FIG. 7. In either event, at least a portion ofthe grooves 292, 294 are disposed along the distal ends 296, 298,thereby essentially eliminating the need to deburr the small end 256 ofthe connecting rod assembly 210 after machining to create the reducedwidth configuration, as described in greater detail below. The grooves292, 294 may also direct lubrication during engine operation to reducefriction and thermal stress at the interface between the piston pin 24and the contact surface 290. While the embodiment of the connecting rodassembly 210 shown in FIG. 7 includes a small end 256 having a steppedconfiguration, those having ordinary skill in the art will appreciatethe small end 256 of the connecting rod assembly 210 may also have atrapezoidal configuration.

Referring to FIGS. 3A-5B, the method of manufacturing the connecting rodassembly 10 of the present invention includes defining the small end 56of the connecting rod having a terminal end 62. The small end 56 may bedefined by any suitable process known in the art. By way of example, thesmall end 56 may be defined via forging, casting or powder metallurgy. Apin bore 64 is also defined at the small end 56 may be preliminarilyformed during this initial step of forging, casting, or powdermetallurgy and later finish machined into the small end 56.

Where forging is employed, the step of defining the small end 56includes heating a metal blank in to temperature where the metal may bepressed, stamped, or pounded into a predetermined form. The metal blankmay then be placed into a die cavity having a predetermined form andsubsequently forged to correspond to the predetermined form of the diecavity. Where casting is employed, the step of defining the small end 56includes pouring molten metal into a mold cavity having a predeterminedform and allowing the molten metal to cool to conform to thepredetermined form of the mold cavity. Where powder metallurgy isemployed, the step of defining the small end 56 includes compressing ametal powder within a die cavity to define a predetermined form andsintering the compressed powder to bond and conform the powder metal tothe predetermined form of the die cavity. Those having ordinary skill inthe art will appreciate that the connecting rod assembly 10 may also bemachined from metal stock.

Once the small end 56 is defined, the method of the present inventionincludes forging a pair of channels 68, 70 on opposite sides 72, 74 ofthe small end 56 such that the axis of each of the channels 68, 70 isperpendicular to the axis of the pin bore 64. Those having ordinaryskill in the art will appreciate that where the forging process isemployed to define the small end 56, the channels 68, 70 may besimultaneously forged therewith. Further, where casting or powdermetallurgy is employed to define the small end 56, the channels 66, 68may be incorporated during either of these processes.

The method of manufacture further includes forming a bushing 84 having acontact surface 90 including at least partially annular grooves 92, 94.The bushing 84 may be formed by any conventional method which mayinclude the methods described above to define the small end 56 of aconnecting rod 10. Accordingly, the above-identified methods areincorporated by reference herein relative to forming the bushing 84.Further, rather than forming the bushing 84 by casting, forging,machining or power metallurgy, the material for the bushing 84 may becast, forged or machined as flat stock and subsequently shaped toconform to the circumference of the pin bore 64. Regardless of theprocess employed to form a bushing, the grooves 92, 94 may be machined,stamped, or otherwise defined within the bushing prior to shapingmachining the small end to provide a reduced width configuration, aswill be described in greater detail below. By way of example, where aflat stock material is employed, the grooves 92, 94 may be formedtherein prior to working the material to conform to the circumference ofthe pin bore 64.

A bushing 84 is then installed into the pin bore 64 of the small end 56.The bushing 84 is positioned in relative proximity to the pin bore 64such that the axis of the pin bore 64 and the axis of the bushing 84 aresubstantially aligned. Specifically, the bushing 84 is positionedadjacent the ridges 76, 78 or 80, 82 of a channel 68 or 70,respectively, and inserted into the pin bore 64 until the bushing 84 issubstantially centered within in the pin bore 64. Insertion occurs bymechanically pressing the bushing 84 into the pin bore 64 to provide aninterference fit between the bushing 84 and the pin bore 64, therebymaintaining the bushing 84 in a fixed position relative to the pin bore64. In order to provide the interference fit between the bushing 84 andthe pin bore 64, the outer diameter of the bushing 84 vary withinmicrometers relative to the inner diameter of the pin bore 64. However,the difference in diameters may not be so great as to compromise thefixed position of the bushing 84 relative to the pin bore 64 necessaryduring engine 12 operation.

The bushing 84 may also be installed into the pin bore 64 by creating atemperature differential between the bushing 84 and the small end 56.Accordingly, heating the small end 56 to provide thermal expansion ofthe pin bore 64 or cooling the bushing 84 to provide thermalcontraction, or both, will affect the desired temperature differentialand assist in the installation process. Specifically, under the effectedtemperature differential, the outer diameter of the bushing 84 willreduce and the inner diameter of the pin bore 64 will expand, therebyenabling the bushing 84 to be inserted within the pin bore 64. Uponachieving temperature equilibrium between the two components, thebushing 84 is fixed within the pin bore 64. Those having ordinary skillin the art will appreciate that the above-identified methods ofinstalling a bushing 84 into a pin bore 64 are exemplary and that thestep of installing a bushing 84 within a pin bore 64 may be accomplishedby several different methods.

Once the bushing 84 is installed into the pin bore 64, a contact surface90 is defined within the small end 56. Referring to FIGS. 4-5B, amachining tool, generally indicated at 300, engages the innercircumference of the bushing 84 to define the contact surface 90 whichfacilitates smooth rotational movement of the piston pin 24 duringengine 12 operation. As shown in FIG. 4, the machining tool 300 includesa rotary driven shaft 302 and a cutting head 304. The cutting head 304includes a plurality of pads 306 which support the cutting head 304during rotational movement within the pin bore 64. The cutting head 304further includes a plurality of cutting faces 308 that define thecontact surface 90. As a result of the channels 68, 70 and the ridges76, 78 and 80, 82 formed therefrom, the machining tool 300 will finishmachine the contact surface 90 to the appropriate inner diameter for aparticular application without incurring the moment forces associatedwith finish machining the contact surface of a small end having areduced width upper region with respect to the remaining portion of thesmall end. Those having ordinary skill in the art will appreciate thatthe contact surface 90 may be defined by any suitable machining tools,such as a CNC machine or other type of cutting tool suitable fordefining a contact surface 90 within the small end 56 of a connectingrod assembly 10.

The small end 56 of the connecting rod assembly 10 is subsequentlymachined to reduce the width between each channel 68, 70 and theterminal end 62, thereby providing a stepped configuration (FIGS. 5A and5B). Specifically, the small end 56 is machined to remove apredetermined portion between the ridges 78, 82 of each channel 68, 70and the terminal end 62. Thus, this machining step acts to substantiallyremove the ridges 76, 80. Whether the bushing is a conventionally shapedbushing or it includes predetermined contours 86, 88 corresponding tothe contour of the channels 68, 70, as described with respect to FIGS.3A and 3B above, a predetermined amount of the bushing 84 is alsoremoved during the machining of the small end 56 to provide the steppedconfiguration.

In particular, during machining of the small end 56, a predeterminedamount of the bushing 84 is removed such that the grooves 92, 94 aredisposed along at least a portion of the distal ends 96, 98. Where atleast a portion of the grooves 92, 94 are disposed along the distal ends96, 98 the need for the small end 56 of the connecting rod 10 to undergoa subsequent deburring process is essentially eliminated.

Similarly, the embodiment of the connecting rod assembly shown in FIG. 6may be manufactured according to the method described above withreference to FIGS. 3A-5B. However, the step of machining the small endof the connecting rod assembly to provide a stepped configuration isreplaced by machining the small end to provide a trapezoidalconfiguration. Specifically, the small end 156 is machined to remove apredetermined portion between the ridges 178, 182 and the terminal end162, thereby substantially removing the ridges 176, 180. Accordingly, bymachining the small end 156 of the connecting rod assembly 110 toprovide a trapezoidal configuration, at least a portion of the grooves192, 194 are disposed along the distal ends 196, 198. Alternatively,where a particular application of the connecting rod assembly 110requires a more pronounced trapezoidal configuration, the small end 156may be machined to remove a predetermined portion of the ridges 178, 180as well as the ridges 176, 182 to provide the desired trapezoidalconfiguration. This alternative method would provide the same advantagesof essentially eliminating moment forces during installation of thebushing 184 and final machining of the contact surface 190 as well asessentially eliminating the need for a deburring process as at least aportion of the grooves 192, 194 are disposed along the distal end 196,198. As shown in FIG. 6, the grooves extend entirely around the distalends 196, 198.

Referring to the embodiment of the present invention shown in FIG. 7,the connecting rod assembly 210 is manufactured according to analternative method of manufacture to that described with respect toFIGS. 3-6. While similar to the method of manufacture described withrespect to FIGS. 3-6, the connecting rod assembly 210 shown in FIG. 7does not include a bushing 84, 184. Rather, the pin bore 264 of thesmall end 256 includes at least partially annular grooves 292, 294adjacent the distal ends 296, 298 of the pin bore 264. The method ofmanufacture represented by the embodiment illustrated in FIG. 7 includesdefining a small end 256 of a connecting rod 210 having a terminal 262and defining a pin bore 264 extending through the small end 256. Thesmall end 256 may be defined by any suitable process known in the artsuch as forging, casting or powder metallurgy, as described aboverelative to FIGS. 3A-6 is incorporated by reference herein. The pin bore264 defined at the small end 256 may also be formed during the initialstep of forging, casting, or powder metallurgy or may be later machinedinto the small end 256.

The method of manufacturing the connecting rod assembly 210 furtherincludes forming a pair of channels 268, 270 on opposite sides 272, 274of the small end 256 such that the axis of each of the channels 268, 270is perpendicular to the axis of the pin bore 264 as described relativeto FIGS. 3-5B and incorporated by reference herein. At least partiallyannular grooves 292, 294 are also formed along the contact surface 290of the pin bore 264 adjacent the distal ends 296, 298. Alternatively,the grooves 292, 294 may be machined into the contact surface 290 in asubsequent step once the small end 256 is defined. However, those havingordinary skill in the art will appreciate that where the forging processis employed to define the small end 256, the grooves 290, 292 may besimultaneously forged therewith. Further, where casting or powdermetallurgy is employed to define the small end 256, the grooves 290, 292may be incorporated during either of these processes and subsequentlymachined to proper specifications for the desired application.

The small end 256 of the connecting rod assembly 210 is then machined toreduce the width between each channel 268, 270 and the terminal end 262,to provide a stepped configuration as described with reference to theembodiment shown in FIGS. 3A-6. Specifically, during machining of thesmall end 256, a predetermined amount of the pin bore 264 is removedsuch that at least a portion of the grooves 292, 294 are disposed alongthe opposed ends of the pin bore 264. Where at least a portion of thegrooves 292, 294 are disposed along the opposed ends of the pin bore264, the need for the small end 256 of the connecting rod 210 to undergoa subsequent deburring process is essentially eliminated.

The reduced width configuration, shown throughout the figures, reducesweight and improves lubrication between the connecting rod assembly 10and the piston 22 to counter the high loads, temperature, gas pressureand inertial forces localized at this area. In the absence of suchheightened properties, the piston 22 and connecting rod assembly 10 mayscuff and ultimately fail. Likewise, it is important to ensure that thepivot point between the piston 22, connecting rod assembly 10 and pistonpin 24 remains resistant to thermal stress and load fatigue whilemaintaining good friction and wear resistant properties during operationof the engine 12.

Accordingly, the method of the present invention overcomes thedisadvantages of the related art and improves the installation of abushing into a pin bore of a connecting rod having a reduced width,small end thereby prolonging the life of the relative components of aninternal combustion engine without undue wear resulting in “out oftolerance” conditions. Further, the pair of channels on opposite sidesof the small end provide a coplanar area adjacent the pin bore that actsto reduce the moment forces generated when installing the bushing intothe pin bore. This reduces the likelihood of deforming the bushing andcreating an irregular contact area between the bushing, the pin bore, aswell as between the bushing and the piston pin. The method of thepresent invention produces a connecting rod having a reduced weight byreducing the width of the small end. Further, the method of the presentinvention reduces the cost of manufacturing by reducing the need forinspection of improper bushing installation within the small end causedby moment force.

To further over come the disadvantages of the related art, the method ofthe present invention improves lubrication and streamlines manufacturingby providing at least partially annular grooves along the contactsurface within the small end of the connecting rod assembly. Inparticular, the grooves are disposed adjacent the distal ends of thesmall end of the connecting rod assembly. As a result of machining ofthe small end, to provide a reduced width configuration, at least aportion of the each groove is then disposed along a distal end of thesmall end of the connecting rod assembly. In this manner, the need tosubsequently deburr the machined area of the small end is greatlyreduced, thereby streamlining the manufacturing process. Lubricationalong the pivot point between the small end and the piston pin is alsoimproved as a result of the location of the grooves after machining toprovide the reduced width configuration.

The present invention has been described in an illustrative manner. Itis to be understood that the terminology that has been used is intendedto be in the nature of words of description rather than of limitation.Many modifications and variations of the present invention are possiblein light of the above teachings. Therefore, within the scope of theappended claims, the present invention may be practiced other than asspecifically described.

What is claimed is:
 1. A method of manufacturing a connecting rodassembly for use within an internal combustion engine comprising thesteps of: compressing metal powder within a die cavity defining thepredetermined form; sintering the compressed powder to bond and conformto the predetermined form of the die cavity such that the metal powderis shaped into a connecting rod; and removing the connecting rod fromthe mold cavity; defining a pin bore extending through the small end ofthe connecting rod and forming a pair of channels on opposite sides ofthe small end of the connecting rod wherein the axis of each of thechannels is substantially perpendicular to the axis of the pin bore;forming a bushing having a contact surface including at least partiallyannular grooves disposed thereon and opposed distal ends; installing abushing into the pin bore of the small end and; machining the connectingrod to reduce the width of the small end between each channel and theterminal end, wherein at least a portion of the grooves are disposedalong the distal ends to reduce the need to deburr the area adjacent thepin bore.
 2. The method as set forth in claim 1 wherein the step offorming a bushing further includes defining predetermined contourswithin the opposed distal ends substantially corresponding to thechannels of the small end of the connecting rod assembly.
 3. The methodas set forth in claim 1 wherein the step of installing a bushing furtherincludes the steps of: heating the small end of the connecting rodassembly to provide thermal expansion of the pin bore to a predetermineddiameter greater than the predetermined outer diameter of the bushingand; cooling the bushing to contract the bushing to a predetermineddiameter less than the predetermined diameter of the small end pin bore.4. The method as set forth in claim 3 wherein the step of installing abushing further includes the steps of: positioning the bushing inrelative proximity to the pin bore of the small end such that the axisof the pin bore and the axis of the bushing substantially align;inserting the bushing into the small end pin bore until the bushing issubstantially centered within the small end pin bore; and affecting atemperature equilibrium between the connecting rod assembly and thebushing to secure the bushing within the small end pin bore of theconnecting rod assembly.
 5. The method as set forth in claim 1 whereinthe step of installing a bushing further includes the steps of:positioning the bushing in relative proximity to the pin bore of thesmall end such that the axis of the pin bore and the axis of the bushingsubstantially align; and inserting the bushing into the small end pinbore until the bushing is substantially centered within the small endpin bore.
 6. The method as set forth in claim 1 wherein said methodfurther includes the step of machining the bushing to define a contactsurface within the small end of the connecting rod assembly thatoperatively engages a piston pin prior to the step of machining theconnecting rod assembly to reduce the width of the small end betweeneach channel and the terminal end.
 7. The method as set forth in claim 1wherein the step of machining the connecting rod assembly furtherincludes the step of removing a predetermined amount of material of theconnecting rod assembly between the pin bore and the terminal end of thesmall end to provide a stepped configuration along the small end of theconnecting rod assembly where the grooves are disposed along at least aportion of the distal ends.